Louis Lacoste (April 3, 1798 – November 26, 1878) was a Quebec notary and political figure. He was a Conservative member of the Senate of Canada from 1867 to 1878. He was born in Boucherville in 1798. He studied law and became a notary, practicing in Boucherville. In 1834, he was elected to represent the county of Chambly in the Legislative Assembly of Lower Canada, serving until 1838. He supported Louis-Joseph Papineau and was arrested in December 1837; he was released in July 1838. He was elected to the Legislative Assembly of the Province of Canada for Chambly in an 1843 by-election; he was reelected in 1844. He did not run in 1848 but was elected again in an 1849 by-election and reelected in 1851. He was elected again in 1858 and resigned in 1861 to run for a seat in the Legislative Co